Use foldLeft to compute the total size of a list of strings:
Here are two variants, the first calls the foldLeft method (note the multiple parameter list, this is used for currying, i.e. partial function application) while the second is using the /: infix operator, which is in fact an overload of foldLeft:
val list = List("foo", "bar", "hello", "world")
list.foldLeft(0)((len, elem) => elem.size + len)//> res0: Int = 16
(0 /: list) {(len, elem) => elem.size + len} //> res1: Int = 16
Write a Censor trait with a method that will replace the curse words Shoot and Darn with Pucky and Beans alternatives. Use a map to store the curse words and their alternatives. Then, load the curse words and alternatives from a file:
The trait expects the curse words dictionary in the file words.txt:
Shoot:Pucky Darn:BeansThe words are loaded line by line, each line is splitted at the : character and the values are stored in the substitions map. The replace method takes a text as input parameter, converts it as a list of words and applies the substitutions by looking up the map.
trait Censor {
val substitutions = new HashMap[String, String]
Source.fromFile("/words.txt", "US-ASCII").getLines.foreach { line =>
val elem = line.split(":", 2)
substitutions += (elem(0) -> elem(1))
}
def replace(text: String): String = {
text.split("\\s").map({word =>
substitutions.getOrElse(word, word)
}).reduceLeft((concat, word) => concat + " " + word)
}
}
Here's a simple example showing how the trait works: val censor = new Censor {}
censor.replace("hello Darn world") //> res2: String = hello Beans world
Stay tuned, I'll soon be posting the 3rd study section about Scala.